Re: Alocasias

It
is my belief that even in the wild forest Alocasia often go through
periods of boom and bust; with the plants reaching a peak of physical
perfection and the often soon afterwards ‘crashing’; the
cycle in the wild seems to be ameliorated by the rejuvenation induced by
regular leaf fall, but in pots there is a real danger that the pieces of the disarticulated
rhizome do not get the chance to rejuvenate before they run out of stored
carbohydrate, and then seem to lose the ability (will?) to re-grow.

Another
factor that is only now becoming clear is that Alocasia, and many other terrestrial
aroids too, I suspect, have some mycrorrhizal association. I first began to
suspect this on finding super-vigorous specimens with infeasibly small root
systems in the wild. Clearly the roots were too small to support the nutrient
uptake that the plants needed, and yet the plants were thriving. The point was
reinforced by observations of litter-trapping Schismatoglottis, notably species
in the S. barbata complex, where investigation of the leaf litter
revealed copious fungal hyphae and significant composting of the oldest leaf litter,
with the plants rooting from the stem and through the leaf bases into this
composted material and the decomposing leaves above. From our experiments we
have observed a beneficial fungal population developing in the leaf litter
within a couple of months, and a notable increase in plant vigour at this time.
In fact, we no longer apply fertilizer to our plants (a considerable saving in
time and money with ca 10,000 individual pots...) and this despite the fact
that the nursery receives 5+ m of rain per anuum, and thus the flow-through of
nutrients from the pots must be considerable.

On
the subject of watering, our plants get watered every day, either from our
virtually daily torrential downpours, or, in ‘dry’ periods from
overhead sprinklers. Even in dry periods humidity seldom drops below 70%. The
key is well-drained media and making sure that the rhizome is not totally
buried. The crucial thing is that the leaf litter layer should not become dry
(leaves crispy). The leaf litter (topmost leaves) remain damp and the leaves
flexible.

One
note, once you get the fungal hyphae community underway, the leaf litter will
decompose fairly quickly. We ‘top up’ the leaves regularly to
ensure that there are always fresh leaves on top of the decomposing and
composted ones.

Many Alocasia literally 'climb' through layers of leaf litter, rooting as
they go, with the older parts of the elongated rhizome gradually senescing
and eventually dying. After much experimentation, and not a few deaths, we
have settled pots half full of a mineral soil (locally produce red topsoil
mixed with river sand in 1:1 mix), with the rhizome at most half buried, and
the remained of the pot filled with leaf litter. The root growth at the leaf
litter/mineral soil interface is extraordinarily vigorous and with the loose
leaves the problem of bacterial rot is resolved. I would suggest that you
try planting our dormant rhizomes in this manner and see what happens.